251
FXUS66 KPQR 050900
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
200 AM PDT Sun Oct 5 2025

.SYNOPSIS...Offshore flow develops today and continues through
early Tuesday morning, bringing an extended period of dry and
breezy conditions with mostly clear skies and high temperatures
in the 70s across the lowlands each day. Temperatures trend
relatively cooler Wednesday onward with increasing chances for
rain. However, forecast uncertainty is high mid to late week.

&&

.DISCUSSION...Sunday through Saturday...Satellite imagery early
Sunday morning shows stratus forming across portions of NW
Oregon and SW Washington due to calm winds and lingering
moisture from recent rains. This stratus should dissipate by
late this morning as offshore winds begin increasing. Building
high pressure over the region along with a surface thermally
induced trough forming along the Oregon and Washington coast
will bring dry and warming conditions through midweek along with
breezy offshore winds this afternoon through early Tuesday
morning. Northerly gusts up to 20-25 mph are expected across
the central and southern Willamette Valley, in the afternoon and
evening hours, strongest this afternoon and evening. East winds
pick up in the late evening to overnight hours over the
Cascades and Cascade foothills with gusts up to 30-35 mph
possible except up to 35-45 mph in the western Columbia River
Gorge. Additionally, high temperatures will warm into the 70s
for inland valleys today through Tuesday. Although atmospheric
conditions will be drying out, causing daytime relative humidity
values to fall quite significantly, the recent rains will limit
any fire weather concerns. Still, those burning should use
caution today through Tuesday morning.

On Tuesday, the high pressure and thermal trough will begin
breaking down later in the day due to an upper level low
pressure system approaching the region This will allow winds to
begin shifting onshore again, though dry and warm conditions
are expected to continue through the day.

The forecast becomes much more uncertain Wednesday onward as
ensemble guidance remains split on how to resolve the
aforementioned upper level low. Looking at the 00z LREF 500 mb
cluster analysis, which is a combination of all GFS, Euro, and
Canadian ensemble members, there is very little change from the
previous few runs. About half of total ensemble members continue
to indicate a closed low deepening right along the Washington
and Oregon coast, while the other half suggests the low will
deepen just west of the coast Wednesday through Friday. The
first scenario would bring the return of cooler temperatures and
shower chances to NW Oregon and SW Washington, whereas the
later scenario would keep conditions dry. However, one
significant change is the temperature forecast spread for
Wednesday is much smaller. The majority of guidance now suggests
inland temperatures will fall into the 60s and remain in the 60s
through Saturday. The deterministic NBM (which our forecast
reflects) continues to introduce a 15-35% chance of rain
Wednesday through Friday, increasing to around 45-60% chance
for Friday night into Saturday. -03

&&

.AVIATION...Stratus is expected to form in patches across NW
Oregon and SW Washington through around 18z Sun. This leads to a
30-40% chance of MVFR ceilings and visibilities at most terminals
except for KEUG which as a 70-90% chance of MVFR/IFR ceilings and
visibilities. Expect conditions to fluctuate between VFR and
MVFR/IFR at most terminals through 18z Sun, except along the coast
where probabilities of lower conditions will diminish through
12-14z Sun and VFR will mainly prevail.

Light and north to northeasterly winds will increase after 18-20z
Sun to around 8-12 kts except for terminals south of KMMV which
could see winds up to 15 kts and gusts up to 20-25 kts, decreasing
after 06z Sun.

KPDX AND APPROACHES...Primarily VFR conditions through the TAF
period. There is a 30-45% chance for IFR/MVFR CIGs between 10-16z
Sun. Light northwesterly winds overnight, shifting northeasterly
and increasing to 8-10 kts after 18-20Z Sunday. -03

&&

.MARINE...High pressure and tightening pressure gradients due to
a thermal trough developing along the coast will shift winds
northeasterly and allow winds to increase today into Monday. A
Small Craft Advisory has been issued for all waters south of Cape
Falcon for a combination of north-northeasterly wind gusts up to
25 kt and choppy seas, beginning 8 AM for the outer waters (beyond
10 NM) and 2 PM for the inner waters (out 10 NM). For the waters
north of Cape Falcon, chances for small craft conditions remain
around 20% or less. Winds remain northeasterly Monday, but will
weaken to less than 20 kts Monday morning. Winds will increase
again in the afternoon and evening hours, but gusts over 21 kts
will be mainly for locations 40-60 NM west of the coast. Seas
around 4-6 ft at 12-13 sec early this morning, with periods
dropping to 8-10 sec later this morning into early next week.
-10/03

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 2 PM this afternoon to 11 PM PDT
     this evening for PZZ252-253.
     Small Craft Advisory from 8 AM this morning to 5 AM PDT Monday
     for PZZ272-273.
&&

$$

www.weather.gov/portland

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